Cumulus-oocyte Complexes Research Articles

Interaction of cumulus-oocyte complex (coc) number, oocyte quality, and blastocyst numbers by repeated ovum pick-up (opu) in in vitro embryo production

Interaction of cumulus-oocyte complex (coc) number, oocyte quality, and blastocyst numbers by repeated ovum pick-up (opu) in in vitro embryo production

Expression of Chitinase-like 3 Protein 1 (CHI3L1) in Buffalo Cumulus-oocyte Complexes during in vitro Maturation

Background: Buffaloes (Bubalus bubalis) are a vital livestock species in South Asia, significantly contributing to milk production and agricultural sustainability. However, reproductive inefficiency remains a significant challenge, adversely impacting productivity. In vitro maturation (IVM) of oocytes is a critical technique for improving reproductive efficiency in buffaloes. Chitinase-3-like Protein 1 (CHI3L1), known for its roles in tissue remodelling and inflammation, has emerged as a potential regulator in reproductive processes. This study investigates the expression of CHI3L1 in buffalo cumulus-oocyte complexes (COCs) during IVM to explore its role in oocyte maturation. Methods: Buffalo ovaries were collected post-slaughter and COCs were retrieved and cultured in TCM 199 medium supplemented with FSH, LH and estradiol. The COCs were classified into immature and mature groups based on morphological criteria after 24 hours of culture. Total RNA was extracted from both groups and CHI3L1 expression was quantified using quantitative real-time PCR (qRT-PCR). Western blot analysis was performed to assess CHI3L1 protein levels in both immature and mature oocytes. Result: The study found a significant upregulation of CHI3L1 expression in mature COCs, with a 3-fold increase compared to immature COCs (p less than 0.05). Western blot analysis confirmed the higher intensity of CHI3L1 protein in mature oocytes, correlating with the qRT-PCR results. These findings suggest that CHI3L1 plays a crucial role in the maturation of buffalo oocytes, potentially through its involvement in tissue remodelling and inflammatory responses within the COCs.

Decreased neurotensin induces ovulatory dysfunction via the NTSR1/ERK/EGR1 axis in polycystic ovary syndrome.

Polycystic ovary syndrome (PCOS) is the predominant cause of subfertility in reproductive-aged women; however, its pathophysiology remains unknown. Neurotensin (NTS) is a member of the gut-brain peptide family and is involved in ovulation; its relationship with PCOS is unclear. Here, we found that NTS expression in ovarian granulosa cells and follicular fluids was markedly decreased in patients with PCOS. In the in vitro culture of cumulus-oocyte complexes, the neurotensin receptor 1 (NTSR1) antagonist SR48692 blocked cumulus expansion and oocyte meiotic maturation by inhibiting metabolic cooperation and damaging the mitochondrial structure in oocytes and surrounding cumulus cells. Furthermore, the ERK1/2-early growth response 1 pathway was found to be a key downstream mediator of NTS/NTSR1 in the ovulatory process. Animal studies showed that in vivo injection of SR48692 in mice reduced ovulation efficiency and contributed to irregular estrus cycles and polycystic ovary morphology. By contrast, NTS partially ameliorated the ovarian abnormalities in mice with dehydroepiandrosterone-induced PCOS. Our findings highlighted the critical role of NTS reduction and consequent abnormal NTSR1 signaling in the ovulatory dysfunction of PCOS, suggesting a potential strategy for PCOS treatment.

Bisphenol A impairs oocyte maturation by dysfunction of cumulus cells

Bisphenol A (BPA) is a well-known environmental endocrine disruptor that has detrimental effects on reproduction. This study aimed to investigate whether BPA exposure could disrupt the function of cumulus cells and influence oocyte maturation and development. Porcine oocytes at the germinal vesicle stage were exposed to BPA for 44 h. The results revealed that BPA exposure led to dysfunction in cumulus cells by inhibiting meiotic division, inducing endoplasmic reticulum stress, and disrupting steroid synthesis. Furthermore, BPA exposure significantly increased reactive oxygen species and caused abnormal distribution of mitochondria in the oocytes. Notably, matured oocytes in the MII stage from the BPA-exposed groups showed significantly reduced development to the blastocyst stage, along with increased autophagy and apoptosis. These findings suggest that cumulus-oocyte complexes are sensitive to BPA exposure during the germinal vesicle stage, and the toxic effects of BPA on cumulus cells can severely inhibit oocyte and parthenogenetic embryos development.

Fertility and early embryonic development in a CD46-edited Gir heifer with reduced susceptibility to BVDV.

Bovine viral diarrhea virus (BVDV) infection during pregnancy is a significant contributor to reproductive failures in cattle. The bovine receptor for BVDV (CD46) was previously edited with a six amino acid substitution (G82QVLAL to A82LPTFS) and shown to have significantly reduced BVDV susceptibility in a Gir heifer calf. Since a role for CD46 has been proposed in mammalian fertilization, our objective was to assess the edited heifer's fertilization rates, early embryonic development, and germline transmission conformation of the edit. Cumulus oocyte complexes were collected from the edited heifer and unedited females, fertilized with semen from an unedited bull and cultured until the blastocyst stage. Ultrasound examinations and serum progesterone concentration were also monitored to confirm estrous cyclicity in the CD46-edited heifer. Estrous cyclicity was normal with visualization of a corpus luteum and elevated progesterone concentrations. Fertilization rates and blastocyst development were not different in oocytes from edited and unedited controls. Genome sequence analysis of blastocysts confirmed germline transmission of either edited allele from the heifer. Subsequently, the CD46-edited heifer was artificially inseminated with semen from an unedited Gir bull and fertility status was confirmed with a diagnosed conception at day 35 of gestation. Thus, a six amino acid substitution in CD46 did not negatively affect fertilization of edited oocytes or early embryonic development when fertilized with semen from an unedited bull. An edited bull is still needed to similarly evaluate reproductive function of sperm cells carrying this CD46 edit.

Association of growth differentiation factor 9 expression with nuclear receptor and basic helix-loop-helix transcription factors in buffalo oocytes during in vitro maturation.

Growth differentiation factor 9 (GDF9) is an oocyte-specific paracrine factor involved in bidirectional communication, which plays an important role in oocyte developmental competence. In spite of its vital role in reproduction, there is insufficient information about exact transcriptional control mechanism of GDF9. Hence, present study was undertaken with the aim to study the expression of basic helix-loop-helix (bHLH) transcription factors (TFs) such as the factor in the germline alpha (FIGLA), twist-related protein 1 (TWIST1) and upstream stimulating factor 1 and 2 (USF1 and USF2), and nuclear receptor (NR) superfamily TFs like germ cell nuclear factor (GCNF) and oestrogen receptor 2 (ESR2) under three different in vitro maturation (IVM) groups [follicle-stimulating hormone (FSH), insulin-like growth factor-1 (IGF1) and oestradiol)] along with all supplementation group as positive control, to understand their role in regulation of GDF9 expression. Buffalo cumulus-oocyte complexes were aspirated from abattoir-derived ovaries and matured in different IVM groups. Following maturation, TFs expression was studied at 8 h of maturation in all four different IVM groups and correlated with GDF9 expression. USF1 displayed positive whereas GCNF, TWIST1 and ESR2 revealed negative correlation with GDF9 expression. TWIST1 & ESR2 revealing negative correlation with GDF9 expression were found to be positively correlated amongst themselves also. GCNF & USF1 revealing highly significant correlation with GDF9 expression in an opposite manner were found to be negatively correlated. The present study concludes that the expression of GDF9 in buffalo oocytes remains under control through the involvement of NR and bHLH TFs.

ICSI and PGT-A in PCOS phenotype-D patients: a matched case-control study versus idiopathic infertile women.

To assess oocyte competence and embryo chromosomal constitution in phenotype-D PCOS women undergoing ICSI for PGT-A at the blastocyst stage. Retrospective study at a private IVF center. In the period 2013-2021, 58 naïve phenotype-D PCOS women (i.e., oligomenorrhea, ovarian PCO-morphology, and absence of hyperandrogenism) underwent ICSI with ejaculated sperm for PGT-A. These cases were matched to 58 controls selected from 2211 naïve women with idiopathic infertility planned for the same treatment in the same period. The matching variables were age (≈ 36years), BMI (≈ 22), cumulus oocyte complexes (COCs) retrieved (≈ 21-23), and sperm quality (≈ 43-45% men with all sperm parameters > 5th percentile). The primary outcome was euploid blastocyst rate (EBR) per cohort of inseminated oocytes. Maturation rates per COCs and euploidy per biopsied blastocysts were similar. PCOS patients with phenotype-D showed higher fertilization per inseminated oocytes and higher blastulation per zygotes. This resulted into a higher EBR per inseminated oocytes and more euploid blastocysts available for transfer, although these differences adjusted for confounders were not significant. The live birth rate per first euploid transfers was comparable, so were all other outcomes considered. Oocyte competence was not compromised in phenotype-D PCOS women, while good prognosis idiopathic infertile women might have unknown oocyte issues. In case of repeated failures after intrauterine insemination, a timely referral to IVF might represent an efficient strategy, in line with the "one-and-done" approach fulfilling a family planning perspective. Indeed, 22% of the phenotype-D PCOS women had 2 singleton LBs and 76% had surplus oocytes/euploid blastocysts after achieving ≥ 1 live birth.

Assessment of loliolide extracted from Biserula pelecinus, present during in vitro oocyte maturation, on fertilisation and embryo development in sheep

Context As a ‘duty of care’, it is important to test whether new forage plants for ruminants contain secondary compounds (PSCs) that affect reproductive performance. We have previously observed, a posteriori, that the presence of a methanolic extract of Biserrula pelecinus during maturation of sheep oocytes increased fertilisation rate and blastocyst development. This result needed to be verified a priori and, if the outcome was repeated, we needed to identify the plant secondary metabolite responsible. Aims To test whether PSCs from B. pelecinus, when added to the oocyte maturation medium, improve fertilisation rate and blastocyst development; to test whether loliolide is the active molecule produced by B. pelecinus. Methods Methanol–chloroform extracts of B. pelecinus were fractionated using rapid silica filtration and solvents of increasing polarity. Fractions at final concentrations of 0, 100 or 200 μg mL−1 were added to the medium used to mature sheep cumulus–oocyte complexes (COCs) and effects were determined for maturation, subsequent cleavage rate, blastocyst rate, hatching rate, blastocyst efficiency and total blastocyst cell number (TCN). Results Fraction BP-6 at 100 μg mL−1 reduced blastocyst rate (P < 0.05), but had no effect when the dose was doubled to 200 μg mL−1. Further fractionation using semi-preparative high-performance liquid chromatography showed loliolide as the most abundant compound in BP-6. Supplementation of the in vitro maturation medium with loliolide (0, 2.5, 5, 10 and 25 μg mL−1) did not affect any measure of embryo development. All COCs treated with B. pelecinus fractions reached the final stage of embryo development, blastocyst hatching. Total blastocyst cell number was not affected. Conclusion The presence of fractions of B. pelecinus extract during in vitro oocyte maturation can reduce embryo development. Implications In vitro techniques can detect potential effects of forages on reproduction. Some fractions from an extract of B. pelecinus when present during oocyte maturation can reduce embryo development. The abundant PSC, loliolide, was not responsible. There was no indication that a PSC in B. pelecinus improves outcomes.

Chronic psychosocial stress affects insulin-like growth factor 1 and its receptors in mouse ovaries.

Context Chronic psychosocial stress negatively affects folliculogenesis and oogenesis. Intraovarian mechanisms mediating these effects are poorly understood. Aims This work aimed to find out how chronic psychosocial stress affects ovarian IGF1 and its receptor (IGF1R), as well as Igf1 and Igf1r gene expression in cumulus-oocyte complexes (COCs). It also aimed to address possible protective effects of gonadotropin stimulation on IGF1 ovarian signalling. Methods Female CD1 mice experienced chronic psychosocial stress of 11-day isolation followed by overcrowding for 10days. To verify the model, blood corticosterone levels and the quality of oocytes were evaluated in stressed females. The levels of IGF1/IGF1R, blood IGF1 concentration, and expression of Igf1 /Igf1r in the ovaries were compared in stressed and unstressed females. Key results Psychosocial stress caused an elevation of corticosterone level, which was alleviated by gonadotropin treatment. The stressed mice showed a decreased IGF1 level in the ovaries and a decreased expression of Igf1 and Igf1r in COCs. In the unstressed females, gonadotropin injection decreased the expression of Igf1 and Igf1r ; in the stressed females, the same treatment increased Igf1r expression. Neither stress nor ovarian stimulation with gonadotropins affected the serum IGF1 level. Conclusions Psychosocial stress suppresses IGF1 signalling in the ovaries. Gonadotropin treatment modulates these effects differently in stressed and unstressed animals. Implications The results may have translational value for human reproduction. Ovarian IGF1 can be considered a candidate for further improvement of IVF results in women under conditions of chronic stress.

Curcumin protects porcine granulosa cells and mouse ovary against reproductive toxicity of aflatoxin B1 via PI3K/AKT signaling pathway

Aflatoxin B1 (AFB1) is a widespread food contaminant with toxic effects on female reproductive system. This concerns the human public health and the development of the livestock industry. Effective and feasible measures against reproductive toxicity of AFB1 are also unknown. Curcumin has been shown to improve animal production performance and alleviate toxicity of AFB1 in other tissues. The study aimed to reveal the potential mechanism of curcumin in alleviating AFB1 exposure-triggered reproductive toxicity in porcine. Porcine GCs and matured oocytes in vitro and mouse ovary in vivo were cultured as model and then exposed to AFB1 and curcumin. The transcriptomics for porcine GCs was performed. The apoptosis, cell cycle, ROS content and mitochondrial membrane potential level analysis were determined using probe staining and flow cytometry. QRT-PCR and western blotting were analyzed for the genes expression. Oocytes maturation and parthenogenetic activation were performed to evaluate the quality of oocytes. The data showed that AFB1 exposure significantly inhibited porcine GCs viability and exhibited concentration-dependent relationship from 1 to 16 μM. Curcumin supplementation efficiently reversed the inhibition of cell viability. Further analysis indicated that curcumin application alleviated AFB1-exposed porcine GCs and mouse ovary mitochondria dysfunction, oxidative stress, cell cycle arrest, and apoptosis. We found that PI3K/Akt signaling pathway plays a vital role in AFB1-induced porcine GCs toxicity through bioinformatic analysis. The data not only confirmed the correlation of PI3K/Akt signaling pathway and oxidative stress, cell cycle arrest and apoptosis, but also consistent with the results that curcumin supplementation could markedly activate the PI3K/Akt signal inhibited by AFB1. Moreover, curcumin reversed AFB1-impaired cumulus-oocyte complex expansion, oocytes maturation rate, blastocyst rate and formation. Our study demonstrated that curcumin supplementation can protect porcine GCs and mouse ovary from toxicity of AFB1 by targeting the PI3K/AKT signaling pathway and provides a viable treatment approach for AFB1-induced female reproductive toxicity.

Increased in vitro production of bovine embryos resulting from oocyte maturation in the presence of triciribine, a specific inhibitor of AKT

The aim of this study was to evaluate the effect of different concentrations of triciribine, a selective Akt inhibitor, on various aspects of oocyte maturation and on the IVF of bovine embryos. Cumulus-oocyte complexes (COCs) were matured in vitro in medium supplemented with: 0 (control), 1, 5, 10, and 20 μM of triciribine. The nuclear maturation was assessed by staining with acetic orcein, while the cytoplasmic maturation was evaluated by mitochondrial (MitoTracker® Red CMXRos) and lipid droplets distribution (LipidTOX). COCs were fertilized in vitro and cultured for nine days. Cleavage rates, blastocyst production, and hatching rates were determined on days three, seven, and nine of in vitro culture, respectively. Oocytes from COCs treated with 1 μM of triciribine were stained at 3, 6, and 9 h of IVM to determine the inhibitor's involvement in germinal vesicle breakdown. Analysis of variance (ANOVA) of the data was performed and the means were compared using the SNK test at a 5 % significance level. Exposure of COCs to 1, 5, and 10 μM of triciribine did not alter the number of matured oocytes (P < 0.05), a concentration of 20 μM reduced the number of oocytes in MII with a consequent increase in oocytes in MI (P < 0.05). This concentration markedly reduced the number of oocytes with peripheral cortical granules and the rates of cleavage and blastocysts (P < 0.05). On the other hand, when COCs were matured in the presence of 1 μM, there was an increase in the blastocyst rate (P < 0.05), but without altering the timing of meiosis resumption (P < 0.05). It is concluded that the Akt pathway participates in the nuclear and cytoplasmic events of in vitro maturation of bovine oocytes, but through mechanisms that do not interfere with germinal vesicle breakdown. Modulation of Akt activity in bovine COCs during IVM with 1 μM of triciribine increases the in vitro production of bovine embryos.

Effects of Ovarian Stimulation with Gonadotropins in the Conditions of Chronic Psychosocial Stress on the Quality of Murine Oocyte

Chronic psychosocial stress may negatively affect the female reproductive system. Meanwhile, the effect of ovarian stimulation with gonadotropins during stress on the quality of oocytes remains poorly studied. The purpose of this work was to investigate the effects of chronic psychosocial stress on the quality of murine cumulus-oocyte complexes during natural estrus cycle, as well as during ovarian stimulation with exogenous gonadotropins; the latter is an important part of modern assisted reproductive technologies. The results of the study demonstrate that psychosocial stress does not affect the number of ovulating oocytes, but worsens their quality, i. e. reduces the percentage of mature oocytes. In addition, stressed mice exhibited the increased accumulation of reactive oxygen species in oocytes, which is accompanied by the enhanced rate of apoptosis in cumulus cells. Hormonal stimulation of the ovaries with gonadotropins alleviates the negative changes associated with the psychosocial stress, normalizing the level of reactive oxygen species in oocytes and reducing the rate of apoptosis in cumulus cells.

The Immediate Partial Removal of Cumulus-Oocyte Complexes: A Refined Approach for Rapid Observation of In Vitro Fertilization.

Despite the rapid advancements in clinical and laboratory technologies for in vitro fertilization (IVF), a significant proportion (10%-15%) of patients continue to experience fertilization disorders, leading to low fertilization rates and the production of nonviable embryos. Short-term fertilization involves the early removal of granulosa cells to observe the extrusion of the second polar body, enabling the assessment of fertilization and early remedial measures to address low fertilization rates and complete fertilization failure. However, the observation of short-term fertilization in IVF is impeded by challenges such as excessively large unprocessed clusters of cumulus-oocyte complexes and adhesion between eggs, necessitating complex external procedures for granulosa cell removal, and prolonged observation duration. To tackle this issue, this study proposes a method of immediate partial removal of granulosa cells post egg retrieval. This approach streamlines subsequent stages of short-term fertilization and traditional fertilization monitoring, reduces the time needed for oocyte extrusion, minimizes the likelihood of external environmental impacts on the oocytes, and decreases the risk of missing the critical fertilization observation window. Consequently, the study yields novel clinical evidence aimed at enhancing the operational efficiency of embryonic laboratories in IVF.

Efficiency of oocytes retrieval during a repeated series of transvaginal ultrasound-guided puncture of follicles in Simmental heifers

The article presents data on the efficiency of a repeated series of transvaginal ultrasound-guided recovery of oocytes (OPU) in donor heifers of the Simmental breed. Two series were performed — five OPU sessions with an intensity of once a week and a two-week rest period between series. During the repeated series of OPUS, 1.7 fewer follicles were visualized in donor heifers on average per session compared to the value of this indicator established in the first series (7.0 versus 5.3 follicles, p &lt; 0.05). A decrease in the number of ultrasound-visible follicles during repeated series at the trend level was noted in all five OPU sessions. During the repeat series, 0.4 fewer oocyte-cumulus complexes (OCCs) were obtained from one donor on average per session (3.1 versus 2.7 OCCs). There were no differences in the quality of OCCs between the two OPU series: the proportion of OCCs suitable for further use was 67.0% and 63.5%, respectively, while in individual OPU sessions the differences between the series were multidirectional. Fertilization of oocytes and further in vitro cultivation showed a significantly higher degree of the first division — crushing during the 1st series of OPU (p &lt; 0.05), however, these differences were leveled with further cultivation: the yield of blastocysts was, respectively, 23.6% and 21.7%. Considering the absence of significant differences in the quantitative characteristics of the obtained oocytes, as well as their developmental competencies in vitro, conducting a repeat series of OPU after a two-week rest period may be recommended for obtaining oocytes in donor heifers of the Simmental breed.

Gene expression levels in cumulus cells are correlated with developmental competence of bovine oocytes

The generation of mammalian embryos by in vitro culture is hampered by the failure of many of the embryos to develop to the blastocyst stage. This problem occurs even when cumulus–oocyte complexes (COCs) with good morphology are visually selected and used for culture. Because cumulus cells are important for oocyte maturation and subsequent embryo development, here we compared gene expression patterns in cumulus cells of COCs that developed in vitro to the blastocyst stage with those of COCs that failed to develop. Cumulus cells were aspirated from bovine COCs selected for in vitro culture. Oocyte developmental competence was evaluated by screening for cleavage and development to the blastocyst stage. The collected cumulus cells were used to quantify mRNA levels of FSH receptor (FSHR), insulin-like growth factor-1 receptor (IGF-1R), anti-Müllerian hormone (AMH), AMH receptor II (AMHRII), epidermal growth factor receptor (EGFR), estrogen receptor β (ERβ), B cell lymphoma/leukemia-2 associated X (Bax), and cysteine-aspartic acid protease-3 (Caspase-3). We found that the expression levels of FSHR, IGF-1R, AMH, and EGFR were higher in cumulus cells from COCs that developed to blastocysts as compared with those that failed to develop, whereas expression levels of Bax and Caspase-3 were lower in cumulus cells of COCs that matured to the blastocyst stage. Positive correlations were found between FSHR and IGF-1R expression (r = 0.59) and between ERβ and EGFR expression (r = 0.43) in cumulus cells from COCs that developed to the blastocyst stage. Our findings indicate that gene expression levels in cumulus cells are correlated with the developmental competence of bovine oocytes. Measurement of gene expression in cumulus cells therefore offers a non-invasive means of predicting oocyte developmental competence.

The dose-dependent dual effects of alpha-ketoglutarate (AKG) on cumulus oocyte complexes during in vitro maturation

In this study, we reported for the first time the dose-dependent dual effects of Alpha-Ketoglutarate (AKG) on cumulus oocyte complexes (COCs) during in vitro maturation (IVM). AKG at appropriate concentration (30 µM) has beneficial effects on IVM. This includes improved cumulus expansion, oocyte quality, and embryo development. These effects are mediated through multiple underlying mechanisms. AKG reduced the excessive accumulation of reactive oxygen species (ROS) in cumulus cells, reduced the consumption of GSH and NADPH. Cumulus GSH and NADPH were transported to oocytes via gap junctions, thereby reducing the oxidative stress, apoptosis and maintaining the redox balance in oocytes. In addition, AKG improved the mitochondrial function by regulating the mitochondrial complex 1 related gene expression in oocytes to maintain mitochondrial membrane potential and ATP production. On the other hand, oocyte generated GDF9 could also be transported to cumulus cells to promote cumulus expansion. Conversely, a high concentration of AKG (750 µM) exerted adverse effects on IVM and suppressed the cumulus expansion as well as reduced the oocyte quality. The suppression of the cumulus expansion caused by high concentration of AKG could be rescued with GDF9 supplementation in COCs, indicating the critical role of GDF9 in IVM. The results provide valuable information on the variable effects of AKG at different concentrations on reproductive physiology.Graphical abstract

NPR3 is regulated by gonadotropins and modulates bovine cumulus cell expansion.

The significant role of C-type natriuretic peptide (CNP) and its receptor 2 (NPR2) in regulating oocyte meiotic maturation and facilitating communication between oocytes and surrounding cumulus cells has been well-documented in various mammalian species, including mice, cattle and swine. However, further investigation is needed to ascertain whether natriuretic peptide receptors (NPRs) are involved in regulating other essential ovarian functions. Hence, this study aimed to explore the potential involvement of NPRs in the regulation of cumulus expansion and oocyte meiotic maturation in bovine cumulus-oocyte complexes (COCs). The findings revealed that NPR3 mRNA abundance was downregulated by FSH and LH in cumulus cells of bovine COCs during in vitro maturation (IVM), while NPR2 mRNA levels were not affected by gonadotropins. Inhibition of the epidermal growth factor receptor (EGFR) during IVM of COCs prevented the NPR3 mRNA downregulation induced by gonadotropins in cumulus cells. Additionally, treatment of COCs during IVM with an NPR3 agonist (cANP4-23) inhibited cumulus expansion induced by gonadotropins. This inhibitory effect was further intensified when COCs were co-treated with cANP4-23 and CNP. These findings provide robust evidence indicating that normal cumulus expansion in bovine COCs involves an inhibitory effect of gonadotropins on NPR3 mRNA expression, which is mediated via EGFR signaling. The study also provides evidence that CNP and NPR3 interact synergistically to regulate cumulus expansion in response to gonadotropins.

Comparative analysis of short versus long co-incubation of gametes on post-insemination outcomes and embryo morphokinetics: a sibling oocyte randomized study

Research questionDoes a short co-incubation of gametes in conventional IVF impact post-insemination outcomes and embryo morphokinetics? DesignSibling oocyte randomized pilot study performed between December 2020 and March 2023. Eligible couples (n=55) were female aged 18-43 years with body mass index (BMI) ≤35 and male normal semen parameters. Cumulus oocyte complexes (COCs) (min 6 - max 12) were randomized in a 1:1:2 proportion in long (16-18 hrs), or short (2 hrs) co-incubation IVF exposure, and ICSI, respectively. All oocytes inseminated via IVF were monitored by time-lapse (TL). Blastocysts of ≥BL3CC were subjected to trophectoderm (TE) biopsy on day (D)5, D6 or D7 by next generation sequencing (NGS). ResultsA total of 954 COCs were distributed to long co-incubation (n=235, 24.6%), short co-incubation (n=235, 24.6%), and ICSI (n=484, 50.3%). In total, 202 were MII after long co-incubation, 209 after short co-incubation and 394 at ICSI. Regression analyses showed both short co-incubation groups (OR: 0.72, 95% CI: 0.46–1.11, P=0.139) and ICSI (OR: 1.43, 05% CI: 0.95–2.15, P=0.090) did not significantly impact normal fertilization rates (2PN) when compared to long co-incubation. Usable blastocysts per MII, per 2PN, and euploid blastocysts per MII, per 2PN and per tested blastocysts were similar among the groups. The rate of embryo arrest (HR: HR: 0.79, 95% CI: 0.57-1.11, P=0.183) and timings to reach morphokinetic milestones among embryos reaching blastulation were similar between IVF groups (P>0.05, for all). ConclusionA short 2-hour co-incubation of gametes in IVF yields comparable fertilization, blastocyst, and euploidy rates without adverse embryo morphokinetic events, compared to standard overnight co-incubation.

New Insights on In Vitro Maturation of Oocytes for Fertility Preservation

In the last decade, the evolution of oncofertility has sparked a resurgence of interest in in vitro maturation (IVM) due to its suitability in certain oncological scenarios where controlled ovarian hyperstimulation may not be feasible. The retrieval of immature cumulus–oocyte complexes from small antral follicles, regardless of the menstrual cycle phase, presents a swift opportunity to vitrify mature oocytes or embryos post-IVM in urgent situations or when stimulation is not advisable. Harvesting immature cumulus–oocyte complexes and immature oocytes can be achieved transvaginally or directly in the laboratory from extracorporeal ovarian tissue. Although IVM has transitioned from an experimental status due to safety validations, it relies on the intricate process of oocyte maturation. Despite successful live births resulting from IVM in fertility preservation contexts, the comparatively lower developmental competence of in vitro matured oocytes highlights the necessity to enhance IVM culture systems. Recent advancements in IVM systems hold promise in bolstering oocyte competence post-IVM, thereby narrowing the gap between IVM and outcomes from ovarian stimulation. Additionally, for optimizing the chances of conception in cancer survivors, the combination of IVM and ovarian tissue cryopreservation stands as the favored choice when ovarian stimulation is unfeasible.

Lack of effect of cAMP modulation during pre-maturation in vitro on development to the blastocyst stage and expression of specific genes associated with lineage commitment

Pharmacological elevation of cAMP of cultured cumulus-oocyte complexes (COC) before or coincident with initiation of maturation has been reported to improve outcomes for various systems for in vitro production of embryos. Here it was hypothesized that artificial elevation of cAMP in the oocyte for a 2-h period of pre-maturation would improve developmental competence of matured oocytes and result in increased blastocyst yield and alter expression of genes important for embryonic differentiation. Treated COC were cultured for 2 h with dibutyryl cAMP (dbcAMP), a membrane-permeable form of cAMP, and 3-isobutyl-1-methylxanthine (IBMX), which inhibits phosphodiesterases that convert cAMP to ATP. Subsequently, oocytes were matured and fertilized and the resultant embryos cultured for 7.5 d. There was no effect of treatment on the percent of oocytes or cleaved embryos becoming blastocysts or on transcript abundance of EOMES, GATA4, NANOG, SOX2, or SOX17 in the blastocyst. Results do not support the use of pharmacological enhancers of cAMP concentrations in the oocyte for improving the blastocyst yield following in vitro oocyte maturation, fertilization, and embryo culture.